Korean Adoptee searching for birth family, adopted May, 1976

I am searching for my birthfamily in Korea. I believe my father and siblings are still living in Korea. I was adopted through a charity organization and arrived in Minneapolis, Minnesota on May 2, 1976. I was given up by my mother and put into an orphanage. My mother didn't want to give me up but had to. On my greencard I was born on 4/1-1972, however I think I was born on 1969. Can anyone help me! I'm desperate to find my roots.